1. Field of the Invention
This invention relates to a developing apparatus for a one component type toner.
2. Description of the Prior Art
As one of the general methods for developing nonmagnetic one component type toners, there has usually been proposed a developing method comprising the steps of laminating the toner on a toner holder (namely, a developing roller) by means of a blade-shaped or roller-shaped element, and abutting the same on a photosensitive element that has formed electrostatic latent images thereon. In this instance, the thin film-forming element has been required to have such properties as releasability to toner, abrasion resistance, chargeability to toner and the like. Therefore, a metal such as stainless steel or the like, a fluorine-containing resin, a denatured fluorine-containing resin or the like has been employed. However, the metal has been very defective in that since the metal is very inferior in the releasability to toner, the toner adheres onto the abutting surface, stripes take place on the thin toner layer, and said stripes appear on the image taking the form of white stripes. In the case of the element formed of the fluorine resin or the like, it has been defective in that said element is short-lived because it is superior in the releasability to toner but very inferior in abrasion resistance, and that since it is so strong in the minus chargeability, it is easy to positively charge the toner but is difficult to negatively charge the toner, whereby said element is difficult to use in common with both plus and minus toners. Further, even when using the denatured fluorine-contained resin, that is a copolymer with another resin represented by polyethylene or the like, as an improved fluorine-contained resin, the abrasion resistance and the chargeability to toner are somewhat improved but the releasing ability deteriorates, thereby causing the toner to adhere.
Next, it is seen from Japanese Laid-Open Patent Application No. 66442/1982 that even when using the silicone resin, denatured silicone resin and silicone oil as the friction charging element, it was inferior in the points of abrasion resistance and releasing ability to toner.
In view of the aforegoing, there has been demanded an element that is capable of simultaneously satisfying the various characteristics required for the toner thin film-forming element, particularly those such as abrasion resistance, releasing ability to toner and chargeability to toner.